Device for regulating the rate of flow of recycled exhaust gases in an internal combustion engine

ABSTRACT

In an internal combustion engine equipped with a mechanism for recycling the exhaust gases, or at least a fraction thereof to dilute the fresh mixture, the improvement consisting in providing means for sensing the pressure drop of the gases in the exhaust duct, means for sensing the pressure drop in the auxiliary duct intended for recycling the exhaust gases, and a member being provided for establishing a proportionality ratio between the respectively sensed pressure drops.

United States Patent Garcea 51 Oct. 29, 1974 DEVICE FOR REGULATING THERATE OF FLOW OF RECYCLED EXHAUST GASES IN AN INTERNAL COMBUSTION ENGINE[75] Inventor: Giampaolo Garcea, Milan, Italy [73] Assignee: Alia-RomeoS.p.A., Milan, ltaly [22] Filed: Feb. 5, 1973 [21] Appl. No.: 329,822

[30] Foreign Application Priority Data Feb. 8, 1972 Italy 20344/72 [52]US. Cl 123/119 A [51] Int. Cl. F02m 25/06 [58] Field of Search 123/119 A[56] References Cited UNITED STATES PATENTS 3,507,260 4/1970 Walker123/119 A 3,675,633 7/1972 Nakajima et al 123/119 A PrimaryExaminer-Wendell E. Burns Attorney, Agent, or Firml-lolman & Stern [57]ABSTRACT In an internal combustion engine equipped with a mechanism forrecycling the exhaust gases, or at least a fraction thereof to dilutethe fresh mixture, the im provement consisting in providing means forsensing the pressure drop of the gases in the exhaust duct, means forsensing the pressure drop in the auxiliary duct intended for recyclingthe exhaust gases, and a member being provided for establishing aproportionality ratio between the respectively sensed pressure drops.

7 Claims, 4 Drawing Figures DEVICE FOR REGULATING THE RATE OF FLOW OFRECYCLED EXHAUST GASES IN AN INTERNAL COMBUSTION ENGINE BACKGROUND OFTHE INVENTION It is known that one of the methods which is beinginvestigated in order to diminish the percentage of nitrogen oxides inthe exhaust gases of internal combustion engines consists in dilutingthe charge of fresh mixture with burned gases taken from the exhaustduct. This expedient is an asset since, by so doing, the maximumtemperatures of the ycle (their value influences the formation ofnitrogen oxide) are decreased.

The amount of exhaust gas taken downstream of the engine incorrespondence with the exhaust duct and suitably cooled, which isrequired, should be introduced upstream of the engine. In order toprevent deposits and fouling in the carburetor, in the engines equippedwith a carburetor, it is advisable to effect this exhaust gas feeddownstream of the carburetor, between the carburetor and the inductionvalve. However, as compared with the other approaches (such as theintroduction of gases upstream of the carburetor), this solutioninvolves a greater difficulty as regards the regulation of the amount ofexhaust gas to be intro duced; as a matter of fact, downstream of thecarburetor and thus of the throttle, the pressure undergoes aconsiderable variation according to the conditions of use of the engineand the amount of exhaust gases tends to be extremely high when thethrottle is partially closed under conditions of highly negativepressures whereas, on the contrary, it is very small when the throttleis fully open. This tendency is the exact contrary of what would bedesirable: as a matter of fact, nitrogen oxides are formed in theexplosion chamber prevailingly at high power deliveries whereas they arenegligible when the engine is idling and delivers only reduced powers.

SUMMARY OF THE INVENTION A first embodiment of the device according tothe present invention has for its object to render the dilution ratio ofthe fresh mixture to the exhaust gases constant irrespective of theconditions of use of the engine in the operative range which is ofinterest; such an approach is, in fact, considered to be satisfactory asitself.

The device is based on the idea that, with a fair degree ofapproximation, if one maintains constant the ratio between the rate offlow of the exhaust gases introduced in the mixture (that is, recycledexhaust) and the overall rate of flow of exhaust gases, also thedilution ratio (that is, the ratio between the rate of flow of therecycled gas and the rate of flow of fresh mixture) remains constant.This idea is fully valid if the admixture ratio (intended as the ratiobetween the rate of flow of air and the rate of flow of fuel drawn bythe engine) remains constant under the difi'erent conditions of use, butthe variations of the admixture ratio are generally so slight as to haveno determining bearing on a regulation carried out in this way.

An object of the present invention is to provide a particularly simpleand reliable device for regulating the rate of flow of the recycledgases so that it may be in a substantially constant ratio with the rateof flow ofthe exhaust gases and thus, finally, with the rate of flow ofthe gases drawn by the engine.

According to the invention, an internal combustion engine, equipped withan intake duct, an exhaust duct and an auxiliary piping connected tosaid exhaust duct to draw a portion of the gases flowing therethrough todischarge them into said intake duct, is characterized in addition byfirst means sensitive to the pressure drop undergone by the gasesflowing through at least a portion of said exhaust duct, by second meanssensitive to the pressure drop undergone by the gases flowing through aportion of said auxiliary piping, and by a throttling member for saidauxiliary piping which is driven to move by said first and said secondmeans in the sense of keeping the sensed pressure drops proportional toeach other, respectively.

It is well known that the pressure drops in a duct are proportional tothe square power of the rate of flow (by volume) of the flowing fluid,and on the basis of said principle, the consequence is that theconstancy of the ratio between the pressure drops sensed by said firstand said second means, or their mere equality, ensures the constancy ofthe ratio between the respective rates of flow, in the exhaust duct andthe recycle piping, according to the objects of the present invention.

The foregoing objects and features of the present invention can bebetter understood from the ensuing description of exemplary embodimentsthereof as illustrated in the accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows as a diagrammaticaloverall view an internal combustion engine according to the invention,

FIG. 2 shows a cross-sectional view of a detail of FIG. 1, and

FIGS. 3 and 4 show modifications to the detail illustrated in FIG. 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS In FIG. 1, the numeral indicatesan internal combustion engine having four in-line cylinders shown at 11,12, l3, 14: the numeral 15 indicates the induction duct of the engineand 16 is the intake manifold from which branch off the individualintake ducts of the several cylinders. The numeral 17 indicates the bodywhich contains the throttling members of the fluid drawn by the engine:a mixture in the case of an engine having a carburetor, and air in thecase of an injection engine. The linkage mechanism of said throttlingmembers, which is known as itself, is partly shown, with the acceleratorpedal of the vehicle: the drawing shows a lever 18 connected to thethrottling members and a rod 19 connected to an accelerator pedal (notshown). The numeral 20 indicates the filter, having also a silencingfunction for the air drawn from the outside by the engine. There areshown at 21, 22, 23, 24 the exhaust ducts coming from the individualcylinders and 25 is a manifold to which is flangedly connected at 26 aduct 27 which sends the gas to the outside.

In the duct 27 are arranged a postcombustion muffler 28 and a silencermuffler 29.

There are shown at 30 and 31 two small ducts which start from the duct27, the former from a point upstream of the muffler 28, and the latterfrom a point downstream of the muffler 29.

The duct 31 opens into a chamber or space 37 whose constructionalfeatures are best seen in FIG. 2: the duct 30 is connected through theflange 32 to the counterflange 33 of a cylindrical section 34 which isjointed to -a duct 35 opening into the induction duct 15.

From the cylindrical section 34 branches off a small tube 36 connectedto the space 37.

In FIG. 2 there is shown in its constructional details the chamber 37along with the cylindrical section 34 located between the ducts 30 and35. There are indicated at 58 and 59 the arrows which show the directionof flow of the recycled gas. There is indicated at 38 a diaphragm havingan opening 39 defining a choke or constriction whose value is fixed andwhich is inserted in the duct 30 by means of the flanges 32 and 33, andat 40 there is a butterfly valve pivoted at 41 to the walls of thesection 34.

To the body of the valve 40 there is hingedly attached at 42 one end ofa rod 43, the other end of the same rod being hinged at 44 to thecentral rigid portion 46 of a movable wall or diaphragm 45. Theperipheral edge of the wall 45 is inserted between the flanges of tworigid half shells 4'7 and 48 of the chamber or space 37, which are keptassembled by a clamping ring 49. There are indicated at 50 and 51 thecavities confined by the movable wall 45 and by the walls of the halfshell 48 and by the same movable wall 45 and the walls of the half shell47, respectively.

The operation of the device described above is as follows: it isapparent that the diaphragm 45 is in equilibrium when the pressureobtaining in the duct 27, in the point where the duct 31 branches off,is equal to the pressure at the terminal point of the tube 30, where theduct 36 branches off, that is, between the fixed constriction 39 and thethrottle 40: these two pressures are, in fact, those which act on thetwo faces of the diaphragm 45. Obviously, this condition of equalityrequires that the gas pressure drop in the portion of the duct 27between the points where the ducts 30 and 31 branch off is maintainedequal to the pressure drop undergone by the recycled gases by flowingthrough the tube 30 from the point where it branches off from the duct27 to the zone immediately downstream of the choke or constriction 39.

At every variation of both the negative pressure in the manifold and thepressure in the duct 27, the diaphragm 45 is shifted towards a newposition of equilibrium corresponding to a different position of thethrottle 40, so as to maintain a constancy of the ratio between therespective rates of flow of the exhaust and the recycled gases accordingto the objects of the invention.

According to a different embodiment, it is possible to measure thepressure dropthe gases undergo when flowing through the portion of theexhaust duct 27 which extends from the point at which the recycling duct30 branches off to the free discharge into the atmosphere.

In this case the device takes a particularly simple shape, as shown inFIG. 3: the face of the diaphragm which corresponds to the chamber 50,is in direct contact with the atmosphere, so that the duct 3i can beeliminated: the diaphragm 45 is in equilibrium when the pressureobtaining in the recycling duct, between the choke 39 and the throttle40 is equal to the atmospherical pressure: that is to say that thepressure drop the gases undergo when flowing through the tube sectionlocated between the point of branching off of the duct 30 and its freeopening into the atmosphere is equal to the pressure drop undergone bythe recycled gases when flowing through the duct 30 from the startingpoint to a zone immediately downstream of the choke 39: also in thiscase such an equality ensures a constant ratio between the rates of flowof the exhaust gases and the recycled gases.

Numerous changes can be made in the embodiments shown herein: moreparticularly in FIGS. 1, 2 and 3, the pressure drop localized in therecycling pipe, determined by the choke 39, can be obtained in variousways or even avoided, by shaping the duct 30 in such a way that itsresistance to the gas flow gives rise to a pressure drop of the desiredvalue. Obviously, the obtention of the desired resistance with the useof a disc 38 having a calibrated opening permits an initial regulationof the ratio of the rates of flow which is very convenient and accurate.

When a variation is desired of the above cited ratio between the ratesof flow, under particular operative conditions of the engine, it can beprovided to place in the recycling duct an additional throttling member,as in FIG. 4, in which a throttle 55 is shown, which is freely pivotedto the wall of the tube 30 and can be controlled by the action of a rod57 which acts on a lever 56 integral with the throttle.

The throttle 55 can be driven, more particularly, in the sense of beingclosed when the engine is required to deliver very small powers; in sucha case, in fact, it is of minor importance to profit of the recycle ofthe exhaust gases: the mechanical linkage 57 can be connected to usualaccelerator pedal 61, in the sense of closing the throttle when thepedal is released due to the bias of springs 62, or it can be controlledwith a similar action by a device sensitive to the negative pressure inthe intake duct of the engine, in the sense of being closed as themagnitude of the negative pressure is increased.

It is obvious that the throttle 55 when it is being closed, causes anincrease of the resistance to the gas flow in the auxiliary pipe 30,thus causing the rate of flow of the recycled gas to diminish, with theresult being a pressure drop in the pipe 30, which is equal to thepressure drop experienced in the exhaust duct 27. It is obvious that insuch a way as the resistance in the pipe 30 is increased, the ratiobetween the gases recycled in the intake duct and the gases exhaustedfrom the engine is decreased.

What is claimed is:

1. An internal combustion engine provided with an intake duct, anexhaust duct and an auxiliary piping connected to said exhaust duct todraw a portion of the gases flowing therethrough to discharge them intosaid intake duct, the improvement including first means sensitive to apressure drop undergone by the gases which flow through at least aportion of the exhaust duct, second means operably related to the firstmeans and sensitive to a predetermined pressure drop undergone by thegases when flowing through a portion of said auxiliary piping and amember for throttling in a variable manner said auxiliary piping, saidmember being driven by said first and said second means in the sense ofkeeping proportional the respectively sensed pressure drops.

2. The internal combustion engine according to claim 1, in which saidfirst means are sensitive to the gas pressure in a point of the exhaustduct which is downstream of the connection of the auxiliary piping tosaid duct, and are sensitive, to the gas pressure at a point of saidauxiliary piping which is upstream of said member, and drive said memberto throttle said auxiliary piping so as to maintain the sensed pressureproportional to each other.

3. An internal combustion engine provided with an intake duct, anexhaust duct and an auxiliary piping connected to said exhaust duct todraw a portion of the gases flowing therethrough to discharge them intosaid intake duct, the improvement including first means sensitive to apressure drop undergone by the gases which flow through at least aportion of the exhaust duct, second means operably related to the firstmeans and sensitive to a predetermined pressure drop undergone by thegases when flowing through a portion of said auxiliary piping and amember for throttling in a variable manner the auxiliary piping, saidmember being driven by said first and said second means in the sense ofkeeping proportional the respectively sensed pressure drops, said firstmeans being sensitive to the gas pressure in a point of the exhaust ductwhich is downstream of the connection of the auxiliary piping to saidexhaust duct and sensitive to the gas pressure at a point of saidauxiliary piping which is upstream of said member, and drive said memberto throttle said auxiliary piping so as to maintain the sensed pressureproportional to each other, said first means consisting of a deformablediaphragm for separating two chambers, the

first chamber being maintained in communication with a point of saidexhaust duct which is downstream of the connection thereto of theauxiliary piping, the second chamber being maintained in communicationwith a point of said auxiliary piping, said diaphragm being operativelyconnected with said throttling member. in the sense of diminishing theflow cross-section of said auxiliary piping when the pressure in saidfirst chamber is greater than the pressure in said second chamber and ofincreasing the flow-cross-section when the pressure of the secondchamber exceeds that of the first chamher.

4. The internal combustion engine according to claim 1, characterized inthat said exhaust duct opens into the atmosphere and said means aresensitive to the pressure at a point of said auxiliary piping andcontrol said throttling means to maintain the sensed pressure in aconstant proportion with respect to the atmospherical pressure.

5. An internal combustion engine provided with an intake duct, anexhaust duct, and an auxiliary piping connected to said exhaust duct todraw a portion of the gases flowing therethrough to discharge them intosaid intake duct, the improvement including first means sensitive to apressure drop undergone by the gases which flow through at least aportion of the exhaust duct, second means operably related to the firstmeans and sensitive to a predetermined pressure drop undergone by thegases when flowing through a portion of said auxiliary piping and amember for throttling in a variable manner said auxiliary piping, saidmember being driven by said first and second means in the sense ofkeeping proportional the respectively sensed pressure drops, saidexhaust duct opening into the atmosphere and said means being sensitiveto the pressure at a point of said auxiliary piping and controlling saidthrottling means to maintain the sensed pressure in a constantproportion with respect to the atmospherical pressure, said meanscomprising a chamber having a wall consisting of a deformable diaphragmand in communication with a point of said auxiliary piping upstream ofsaid member, the latter being operatively connected to said diaphragm soas to diminish the cross-section of said piping when the pressure insaid chamber is subatmospherical and increasing it when the pressureexceeds the atmospherical pressure.

6. The internal combustion engine according to claim 1, characterized inthat in said auxiliary piping there is arranged a member for varying theresistance to gas flow in said piping.

7. An internal combustion engine according to claim 6, characterized inthat said member is driven to vary said resistance by a sensing memberof the power delivered by the engine in the sense of diminishing theresistance as the power is increased and vice versa.

1. An internal combustion engine provided with an intake duct, an exhaust duct and an auxiliary piping connected to said exhaust duct to draw a portion of the gases flowing therethrough to discharge them into said intake duct, the improvement including first means sensitive to a pressure drop undergone by the gases which flow through at least a portion of the exhaust duct, second means operably related to the first means and sensitive to a predetermined pressure drop undergone by the gases when flowing through a portion of said auxiliary piping and a member for throttling in a variable manner said auxiliary piping, said member being driven by said first and said second means in the sense of keeping proportional the respectively sensed pressure drops.
 2. The internal combustion engine according to claim 1, in which said first means are sensitive to the gas pressure in a point of the exhaust duct which is downstream of the connection of the auxiliary piping to said duct, and are sensitive, to the gas pressure at a point of said auxiliary piping which is upstream of said member, and drive said member to throttle said auxiliary piping so as to maintain the sensed pressure proportional to each other.
 3. An internal combustion engine provided with an intake duct, an exhaust duct and an auxiliary piping connected to said exhaust duct to draw a portion of the gases flowing therethrough to discharge them into said intake duct, the improvement including first means sensitive to a pressure drop undergone by the gases which flow through at least a portion of the exhaust duct, second means operably related to the first means and sensitive to a predetermined pressure drop undergone by the gases when flowing through a portion of said auxiliary piping and a member for throttling in a variable manner the auxiliary piping, said member being driven by said first and said second means in the sense of keeping proportional the respectively sensed pressure drops, said first means being sensitive to the gas pressure in a point of the exhaust duct which is downstream of the connection of the auxiliary piping to said exhaust duct and sensitive to the gas pressure at a point of said auxiliary piping which is upstream of said member, and drive said member to throttle said auxiliary piping so as to maintain the sensed pressure proportional to each other, said first means consisting of a deformable diaphragm for separating two chambers, the first chamber being maintained in communication with a point of said exhaust duct which is downstream of the connection thereto of the auxiliary piping, the second chamber being maintained in communication with a point of said auxiliary piping, said diaphragm being operatively connected with said throttling member. in the sense of diminishing the flow cross-secTion of said auxiliary piping when the pressure in said first chamber is greater than the pressure in said second chamber and of increasing the flow-cross-section when the pressure of the second chamber exceeds that of the first chamber.
 4. The internal combustion engine according to claim 1, characterized in that said exhaust duct opens into the atmosphere and said means are sensitive to the pressure at a point of said auxiliary piping and control said throttling means to maintain the sensed pressure in a constant proportion with respect to the atmospherical pressure.
 5. An internal combustion engine provided with an intake duct, an exhaust duct, and an auxiliary piping connected to said exhaust duct to draw a portion of the gases flowing therethrough to discharge them into said intake duct, the improvement including first means sensitive to a pressure drop undergone by the gases which flow through at least a portion of the exhaust duct, second means operably related to the first means and sensitive to a predetermined pressure drop undergone by the gases when flowing through a portion of said auxiliary piping and a member for throttling in a variable manner said auxiliary piping, said member being driven by said first and second means in the sense of keeping proportional the respectively sensed pressure drops, said exhaust duct opening into the atmosphere and said means being sensitive to the pressure at a point of said auxiliary piping and controlling said throttling means to maintain the sensed pressure in a constant proportion with respect to the atmospherical pressure, said means comprising a chamber having a wall consisting of a deformable diaphragm and in communication with a point of said auxiliary piping upstream of said member, the latter being operatively connected to said diaphragm so as to diminish the cross-section of said piping when the pressure in said chamber is subatmospherical and increasing it when the pressure exceeds the atmospherical pressure.
 6. The internal combustion engine according to claim 1, characterized in that in said auxiliary piping there is arranged a member for varying the resistance to gas flow in said piping.
 7. An internal combustion engine according to claim 6, characterized in that said member is driven to vary said resistance by a sensing member of the power delivered by the engine in the sense of diminishing the resistance as the power is increased and vice versa. 